Announcement

**robbie** · 03-23-2006, 06:10

Re: Was "Cold Cylinder" Now Is Fuel Choice

I've been running av gas for the winter, too cold and too lazy the carry auto fuel out to the hanger.
My IA doesn't want me to use av gas. Makes to much lead .
I have 750 hours on my engine, it see 98% auto gas, still have not top it yet,
Been 20 years since it was topped 1986, 77/80, 75/80,72/80 68/80.
these were taken last Oct.
I think a 50/50 mixture it the way to go. But I hate picking the carbin out of the plugs every year.

**M Towsley** · 03-23-2006, 10:40

Re: Was "Cold Cylinder" Now Is Fuel Choice

Nick,

I've been running mogas almost exclusively for the last year and a half with no problem. When visiting an out-of-town airport I usually top off with 100LL, since that is all they usually have. For the most part, though, I have hardly run any 100LL. If it is in a storage tank/cans you have about six months for mogas, one year for 100LL. I try not to let mogas sit in the carb too long, though I am usually flying weekly if weather allows. It had sat for about six weeks when we had some particulary bad weather recently, and it started on the first flip. Try to read up on the EAA sight about mogas usage, etc. There is good information about the use of mogas on the web. I think some uninformed mechanics would rather tell you not to use it then take the responsibility to read about it and recommend it. Todays litigious society, you know............

**NY86** · 03-23-2006, 11:38

Re: Was "Cold Cylinder" Now Is Fuel Choice

Stuck valves are caused by deposits on the valve stem combined with erosion of the ID of the valve guide. As the deposits build you have a sort of taper pin effect. Often the valve will stick when power is reduced or when the engine is shut down. This is because the clearances get smaller as the head cools.

Lead does not lubricate valves. In factt, lead deposits on the valve stems just contribute to the problem. (Use of TCP reduced the buildup.) What folks are referring to when they talk about lead lubricating valves (even though most of them don't know it) is that a buildup of lead on the sealing face of the valve cushions the valve when it closes and helps prevent (older) valves from welding themselves to the seats. (This is not a problem with hardened seats found in later engines and recent overhauls).

Once the valve sticks, it is unlikely that a long lived fix can be accomplished without at least reaming the guide and cleaning the stem (see "rope trick"). There is antecdotal evicence that use of MMO in the fuel will prevent or cure this, but I see you are already using it. Ultimately, a new valve guide is the answer. The sharp edge of the new guide scrapes the deposits off before they have a chance to cause a problem.

JMO, YMMV

**N96337** · 03-23-2006, 11:40

Re: Was "Cold Cylinder" Now Is Fuel Choice

I think your mechanic is a wise man, and worth all you have to pay him. I worked in an overhaul shop for a couple of years, and usually in the cylinder shop... we could always tell when an engine had run car gas... Car gas has changed drastically in the past 10 years...no matter what they say.
JH

**TimHicks** · 03-23-2006, 14:50

Re: Was "Cold Cylinder" Now Is Fuel Choice

Elaborate, JH, if you would.
What did you see in the cylinders that indicated it had been run on car gas?

**Marv** · 03-23-2006, 18:05

Re: Was "Cold Cylinder" Now Is Fuel Choice

I had a BC12D-1 for several years. All the fuel i used in it was Av gas. 8o octane when i could get it and 100 when i couln not. I had a valve stick, and a old timer helped me get it loose and told me to use mmo. I did and none of the valves ever stuck again as long as i flew it. Marvin Post

**N96337** · 03-23-2006, 19:06

Re: Was "Cold Cylinder" Now Is Fuel Choice

Tim, mostly what we saw was alot of scoring on valves and guides, as well as wear on the whole cylinder. The combustion chambers were usually very clean...a bit too clean (?)..very seldom was a piston much good. I know alot of people run it and swear by it, and no matter what I say here, there's always someone that says he's been running it for years with no problems... and it's not worth getting in a whole big deal about it. I'm an A&P with IA.. have been for over 20 years... and I don't run it. Gas isn't the same as it was when those STC's came out. We used to run regular in our sprayers alot... it isn't anywhere around there anymore.. I'm glad to clean lead out of a plug once in a while.. I know how much the lead keeps the engine from wearing and helps to dissipate the heat.
JH

**fearofpavement** · 03-24-2006, 13:03

Re: Was "Cold Cylinder" Now Is Fuel Choice

Regarding the avgas/mogas position, I have used both extensively and have observed no detrimental effects from either. Let's do some math... A small Continental burning 4.5 gallons per hour over its 1800 TBO is going to burn 8,100 gallons of fuel. With avgas at $4.00 per gallon and mogas at $2.50 there is a $1.50 savings per gallon using mogas. Multiply that times the 8,100 gallons and the savings is $12,150. Your results may vary. For my money, I am going to burn the mogas. I can buy a lot of parts for what I save (if it does make a difference) I am a certified auto and truck engine mechanic in addition to being an A&P and IA. I have seen the inside of lots of engines. I think the fuel burned is a very small factor in engine longevity. Run the engine often and keep clean oil in it. That's the secret in my opinion. (whether it be your 65 Ford Mustang or your Taylorcraft BD-12 (sorry, couldn't help it)

**akroflyer** · 03-26-2006, 04:37

Re: Was "Cold Cylinder" Now Is Fuel Choice

I have been using auto fuel in my planes for 25 years and I have never had any problems or premature engine wear. I always use mmo in the gas and I have never had any valve problems. An old mechanic once told me that using 100LL in low compression engines is like feeding strawberries to pigs.

**ClipWing_T** · 03-26-2006, 09:10

Re: Was "Cold Cylinder" Now Is Fuel Choice

HI guys, I ran a 0-320 PA-20 350 hrs + on mogas with absolutely no problems.
It was a midtime engine and my A&I would shake his head every time we did
a compression check almost 78/80 evey time .I aslo used mmo too.I remember when they did away with 80 octane (the good ol days lol) all of us
were scared the 100 LL was going to RUIN or engines. Our local FBO always
seem to have problems with his C-150's (i.e.cylinder ) ,Maybe the problem was the Continental engines were not that good to begin with. By the way
I own 3 of them . One is on a steady diet of mogas in my J-5 and no problems
yet 240 hrs, SMOH its a 0-200. Save the money buy car gas . IMHO

Mike in Texas

**peerlesscowboy** · 03-26-2006, 10:48

Re: Was "Cold Cylinder" Now Is Fuel Choice

I always used to run 80 octane (red) in my Continental A-65 powered BC-65. Then when I couldn't get 80 anymore I switched to 100LL (blue), thinking if I get too much lead deposits on the plugs I might have to try the mogas "thing" instead but I haven't had any problems with blue avgas so that's what I'm still running. I wonder if the lead deposit fouling problems some experience might be caused by having the mixture control on the ol' Stromberg carb adjusted too rich?

John C. Saubak

**N96337** · 03-26-2006, 11:41

Re: Was "Cold Cylinder" Now Is Fuel Choice

Tim, this was why I usually keep quiet... We had an engine a day come through the various stages of overhaul where I worked... so we got to see lots of them...not just a few. But, go for it... I never said that cargas wouldn't work... it does. It just doesn't work in anything that flies that I own. 'Nuff said.
JH

**ClipWing_T** · 03-26-2006, 12:36

Re: Was "Cold Cylinder" Now Is Fuel Choice

JH you are giving the BEST advice for sure . I think overall AV GAS is the best choice .Safer too, which is the most important thing to worry about.
Trash and cleaniness of mogas always a worry to me.
My 2 cents, Mike

Announcement

Was "Cold Cylinder" Now Is Fuel Choice

Was "Cold Cylinder" Now Is Fuel Choice

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment